Simulated Proton Exchange Membrane Fuel Cell Research Articles

Corrosion Resistance and Conductivity of Ta-Nb-N-Coated 316L Stainless Steel as Bipolar Plates for Proton Exchange Membrane Fuel Cells

The large-scale application of stainless steel (SS) bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs) is mainly limited by insufficient corrosion resistance and electrical conductivity. In this work, Ta-Nb-N coatings were prepared on 316L SS substrates by unbalanced magnetron sputtering to improve corrosion resistance and conductivity. The Ta-Nb-N coatings had a dense structure without obvious defects. In simulated PEMFC cathode environments consisting of 0.5 M H2SO4 + 2 ppm HF at 70 ± 0.5 °C, which is harsher than the U.S. Department of Energy specification, the corrosion current density of Ta-Nb-N-coated BPs was reduced to 2.2 × 10−2 μA·cm−2. Ta-Nb-N-coated samples showed better electrical conductivity than 316L SS, which had an excellent interfacial contact resistance of 9.2 mΩ·cm2. In addition, the Ta-Nb-N-coated samples had a water contact angle of 100.7°, showing good hydrophobicity for water management. These results indicate that Ta-Nb-N coatings could be a promising material for BPs.

Temperature-relevant degradation in amorphous carbon coated SS316L bipolar plates for PEMFC

The corrosion of metallic Bipolar Plates (BPs) has become a key bottleneck in the practical application of proton exchange membrane fuel cells (PEMFCs). Environmental factors inside the PEMFCs significantly accelerate the degradation of electrical conductivity and durability of metallic BPs. In this work, we investigated the corrosion behavior and conductive properties of amorphous carbon coating (a-C) coated SS316L in a simulated PEMFC environment at various operating temperatures. The results showed that the corrosion current density (Icorr) of a-C varied in a range of 2.3–8.7 nA/cm2 when subjected to a temperature range of 40–80 °C. Additionally, the interfacial contact resistance increased from 4.36 to 9.56 mΩ/cm2 with a rise in temperature. The reasons could be ascribed to two aspects. First, the a-C maintained the good chemical stability of sp2/sp3 bonds regardless of temperature changes, favoring remarkable anti-corrosion and good conductivity. Second, the higher temperatures intensified the penetration of corrosive species, accelerating the dissolution process of a-C coated SS316L and leading to substantial corrosion failure.

Investigation of the Performance of Hastelloy X as Potential Bipolar Plate Materials in Proton Exchange Membrane Fuel Cells.

The phase, mechanical properties, corrosion resistance, hydrophobicity, and interfacial contact resistance of Hastelloy X were investigated to evaluate its performance in proton exchange membrane fuel cells (PEMFCs). For comparison, the corresponding performance of 304 stainless steel (304SS) was also tested. Hastelloy X exhibited a single-phase face-centered cubic structure with a yield strength of 445.5 MPa and a hardness of 262.7 HV. Both Hastelloy X and 304SS exhibited poor hydrophobicity because the water contact angles were all below 80°. In a simulated PEMFC working environment (0.5 M H2SO4 + 2 ppm HF, 80 °C, H2), Hastelloy X exhibited better corrosion resistance than 304SS. At 140 N·cm-2, the interfacial contact resistance of Hastelloy X can reach as low as 7.4 mΩ·cm2. Considering its overall performance, Hastelloy X has better potential application than 304SS as bipolar plate material in PEMFCs.

Improved corrosion resistance and interfacial conductivity of a-C/(Ti:C)/Ti nano-thin film for 316L stainless steel bipolar plates

To enhance corrosion resistance and electrical conductivity of metallic bipolar plates for proton exchange membrane fuel cells (PEMFCs), the film containing amorphous carbon (a-C) outer layer, titanium carbon compound (Ti:C) transition layer and titanium (Ti) seed layer has been deposited on the surface of 316L stainless steel (316L SS) by multi-arc ion plating method. Dense and uniform a-C/(Ti:C)/Ti nano-thin film is relatively hydrophobic and approximately 300 nm thick, presenting a clear multilayer structure. The interfacial contact resistance of 316L SS is effectively reduced from 124.97 mΩ·cm2 to 3.97 mΩ·cm2 at 1.4 MPa after modification. Electrochemical corrosion tests are investigated in the simulated cathodic PEMFCs environment (0.5 M H2SO4 and 2 ppm HF at 70 ℃ bubbled with air). Potentiodynamic polarization results reveal that the corrosion potential of a-C/(Ti:C)/Ti film modified sample is 0.23 V (vs. Ag/AgCl) and the corrosion current density is only 0.14 μA·cm−2. The durability of the a-C/(Ti:C)/Ti film was assessed by conducting potentiostatic polarization tests at various applied potentials. After 4 h potential of 0.6 V and 0.8 V (vs. Ag/AgCl) holding tests, the current densities of the modified 316L SS have stabilized at 0.076 μA·cm−2 and 0.098 μA·cm−2, respectively.

Excellent anti-corrosion and conductivity of NbN coated on Ti bipolar plate by controlling N2 flow rates

The metal bipolar plates which play a crucial role in proton exchange membrane fuel cells (PEMFCs) are applied extensively due to their excellent property. However, the degraded corrosion resistance by corrosive ion and the increased interfacial contact resistance by passivation layer under acidic operating environment will affect the efficiency of PEMFCs. Metal nitride can solve that problem in some extent, however, the effect of nitrogen flow rates on the metal nitride formation during coating deposition is unclear. To solve these, NbN coatings with different N2 flow rates were applied to the bare Ti substrate via magnetron sputtering and thereafter studied. Compared with bare Ti substrate, outstanding anticorrosion performance is exhibited for the coated sample, whose corrosion current decreased three orders of magnitude (∼10−8 A/cm2) in simulated PEMFC cathode environment and the interfacial contact resistance decreased to tenth of that bare Ti substrate (∼5 mΩ cm2).

Screening of sealing materials for PEM fuel cell applications based on weight factor method

AbstractThe inexpensive, endurable sealing members are among the key components determining the performance and durability of proton exchange membrane fuel cells (PEMFCs). However, there is a lack of effective in situ measurement to monitor the sealing performance change in the fuel cell operation environment. Therefore, the durability of a sealing material should be assessed previously to its application. The present work investigates four types of commercially available sealing silicone rubbers, and five groups of aging tests are carried out to compare their properties and durability in a simulated PEMFC environment, including compression set, stress relaxation, compression stress–strain, solution soaking, and low‐temperature characterization. Furthermore, to comprehensively evaluate the performance of these four types of silicone rubbers and screen out the most suitable one, a comprehensive evaluation table of sealing materials selection based on weight factor was established through an expert survey method, by which the experimental results of all the silicone rubbers can be weighted and scored. This method can be widely used in the fuel cell industry.

Effects of fluoride ions on corrosion performance and surface properties of SS304 in simulated PEMFC cathodic environments

U.S. Department of Energy (DOE) 2025 target proposes lower cost requirements for bipolar plates. To investigate the applicability of using cost-effective 304 stainless steel (SS304) as bipolar plates in proton exchange membrane fuel cell (PEMFC) and assess its corrosion risk, this work systematically investigates the impact of fluoride ions on corrosion performance and surface properties evolution of SS304 in simulated PEMFC cathodic environments. The electrochemical tests and morphological characteristics of polarized SS304 samples (0.6 V, 5 h) reveal that an increase in F− concentration results in the inability of SS304 to passivate spontaneously and exacerbates the uniform dissolution corrosion. However, all polarized samples can be electrochemically passivated, exhibit no obvious pitting, and form bi-layer semiconductive passive films with stable current densities (0.031–0.166 μA cm−2) lower than 1 μA cm−2, satisfying the corrosion criterion of DOE 2025. Additionally, the ascending of F− concentration reduces surface roughness, while increasing the wettability and interfacial contact resistance (ICR) of the polarized SS304 samples. The ICR of all SS304 samples, with or without polarization test, ranges from 258 to 754 mΩ cm2 fails to meet the relevant DOE 2025 target (<10 mΩ cm2).

Corrosion Behavior of Coated Low Carbon Steel in a Simulated PEMFC Environment.

Here, potential metallic bipolar plate (BP) materials were manufactured by laser coating NiCr-based alloys with different Ti additions on low carbon steel substrates. The titanium content within the coating varied between 1.5 and 12.5 wt%. Our present study focussed on electrochemically testing the laser cladded samples in a milder solution. The electrolyte used for all of the electrochemical tests consisted of a 0.1 M Na2SO4 solution (acidulated with H2SO4 at pH = 5) with the addition of 0.1 ppm F-. The corrosion resistance properties of the laser-cladded samples was evaluated using an electrochemical protocol, which consisted of the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) measurements, and potentiodynamic polarization, followed by potentiostatic polarization under simulated proton exchange membrane fuel cell (PEMFC) anodic and cathodic environments for 6 h each. After the samples were subjected to potentiostatic polarization, the EIS measurements and potentiodynamic polarization were repeated. The microstructure and chemical composition of the laser cladded samples were investigated by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) analysis.

Improved Metaheuristic Algorithms for Optimal Parameters Selection of Proton Exchange Membrane Fuel Cells: A Comparative Study

As a new attempt to design a precise mathematical model for the proton exchange membrane fuel cell (PEMFC), in this paper, three recently-proposed well-established optimizers: horse herding optimization algorithm (HOA), seagull optimization algorithm (SOA) and gradient-based optimizer (GBO) integrated with two newly-proposed effective strategies, namely self-adaptive strategy, and ranking-based updating strategy, have been extensively investigated to accurately estimate the unknown parameters of this model for accomplishing a better output voltage of the simulated PEMFC stacks. Those hybridized algorithms were briefly named HHOA, HSOA, and HGBO. To assess the performance of those proposed algorithms, six common PEMFC stacks were used and their outcomes were extensively compared with the standard algorithms and some of the state-of-the-arts under various performance metrics and the Wilcoxon rank-sum test. The experimental findings show the effectiveness of both HGBO and HSOA in terms of convergence speed and final accuracy; However, HSOA could be more stable. The source code of this study is publicly available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://drive.matlab.com/sharing/d9263036-9f80-4a40-bad9-ad476ed19c69</uri> .

Enhanced corrosion resistance of Ni/Sn nano-electrodeposited metal foam for flow field application in simulated PEMFC cathode environment

Metal foam, with large specific surface area, suffers serious corrosion problems, as flow field in proton exchange membrane fuel cell (PEMFC). Ni/Sn nanoparticles are deposited onto the surface at galvanostatic and gradient current, respectively. The morphology of coated foams is examined by scanning electron microscopy (SEM), coupled with x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The effect of deposited current on its corrosion resistance in simulated PEMFC cathode environment is evaluated by Tafel polarization test, constant potential test and electrochemical impedance spectra. The results show that the coating effectively improved the stability of metal foam in acid environment. A uniform and dense protective film is formed by Ni/Sn electrodeposition at a gradient current density from 0 to 40 mA cm−2. Its corrosion current at 25, 50 and 80 °C, accounts around 38.0%, 47.3% and 46.7%, respectively, of the value of uncoated metal foam. The most positive corrosion current is obtained, −0.12 mA, which is explained to higher coating resistance (Rcoat). No obvious pitting is depicted in the surface morphology after 8 h, which further proves its high corrosion resistance.

Effect of Magnetic Field on Corrosion Behaviors of Gold-Coated Titanium as Cathode Plates for Proton Exchange Membrane Fuel Cells

Effects of the self-induced magnetic fields generated by the operating current of proton exchange membrane fuel cells (PEMFCs) on metal bipolar plates (BPPs) have hardly been noticed while cannot be ignored. Therefore, corrosion behaviors and surface conductivity of gold-coated titanium (Ti/Au) and bare titanium in simulated PEMFC cathode environment under magnetic fields were evaluated by electrochemical tests and interfacial contact resistance measurements. The results indicated a considerable decrease in corrosion current and interfacial contact resistance of as-received Ti/Au, reaching 1/16 and 1/10 of those of bare titanium, respectively. The applied magnetic field also led to a sharp decline in corrosion current of bare titanium but slight increase for Ti/Au. Electrochemical impedance spectroscopy and scanning electron microscopy results suggested that magnetic field significantly facilitated the corrosion durability of titanium and ameliorating the induced pitting due to coating defects on Ti/Au. Compared to results obtained without MF, interfacial contact resistance of titanium after 24 h potentiostatic polarization under MF further increased by 24%, while a decrease by 8% was recorded for Ti/Au. In sum, effects of self-induced magnetic fields on the corrosion of metal BPPs is significant and these results revised for taking magnetic fields effects in account could be more accurate and realistic.

Characterization and properties of NbN–Nb bilayer formed on titanium for bipolar plates

In this study, the NbN/Nb bilayer structure was prepared by duplex-treatment (plasma surface alloying + nitriding) on titanium used as bipolar plates for proton exchange membrane fuel cells (PEMFCs). Niobium coating was deposited on titanium by means of double glow plasma surface alloying technique. Then, a thin NbN layer was created by plasma nitriding. The corrosion resistance and electrical conductivity of samples were measured in simulated PEMFCs environments. The result shows that at an applied potential of 0.6 V the corrosion current density of duplex-treated sample is two orders lower than that of untreated titanium. After corrosion testing at 0.6 V for 4 h, the interfacial contact resistance is 5.1 mΩ cm2 compared with 29.7 mΩ cm2 for untreated titanium.

Superhydrophobic Stainless Steel Bipolar Plates with Fractal Structure for Fuel Cells by Nanosecond Laser Ablation

Bipolar plate (BP) is one of the crucial components in proton exchange membrane fuel cells (PEMFCs). In extreme cold weather, massive vapor condensation happens right at vehicle start‐ups, which likely causes “water flooding” and thus shortens the lifespan of PEMFCs. Herein, a superhydrophobic stainless steel bipolar plate (SH‐SS BP) that is fabricated by nanosecond laser ablation is reported. Through a repeated low‐energy processing strategy, fractal surface microstructure is fabricated, which has not been reported for SS BP. By grafting stearic acid (SA) monolayer, a robust SH‐SS BP is obtained with a contact angle of 151.74°. The fractal microstructure greatly enhances the contact area between SH‐SS BP and membrane electrode assembly (MEA), which improves interfacial contact resistance (ICR: 9.816 mΩ cm2 at 1.5 MPa). The SH‐SS BP shows significantly enhanced anticorrosion performance (= A cm−2) by effectively reducing penetration of corrosive. The ability of improving water management in PEMFC under extreme cold condition is further demonstrated in a simulated PEMFC. This study opens new opportunity to reinforce metallic BPs by a simple, low‐cost, and robust route, which is valuable in improving comprehensive weather fastness of PEMFC.

NbC/Nb Film-Modified Stainless Steel Bipolar Plate for Proton Exchange Membrane Fuel Cell

The NbC/Nb composite film on SS304 as the bipolar plate of proton exchange membrane fuel cell (PEMFC) was prepared by magnetron sputtering deposition. Scanning electron microscopy and x-ray diffraction were used to characterize the morphology and composition of the film. Electrochemical tests under simulated PEMFC operating conditions (pH 3 H2SO4, 0.1 ppm HF at 80°C) show that the NbC/Nb composite film can provide better corrosion resistance. Potentiodynamic polarization tests reveal that NbC/Nb/SS304 shows lower corrosion current density and more positive corrosion potential than Nb/SS304 and SS304 substrate in simulated PEMFC environments. Potentiostatic tests were also performed at the potentials of 0.84 VSHE for 24 h to simulate the cathodic PEMFC conditions. NbC/Nb/SS304 reaches the lowest polarization current density of 1.01 × 10−7 A/cm2, which is lower than Nb/SS304 (1.83 × 10−7 A/cm2) and SS304 (1.11 × 10−4 A/cm2, four orders of magnitude as low). Under the pressure of 140 N/cm2, the interfacial contact resistance value of NbC/Nb/SS is 8.76 mΩ·cm2, which is significantly lower than Nb/SS304 (14.0 mΩ·cm2) and SS304 substrate (224 mΩ·cm2). After 0.84 VSHE potentiostatic polarization for 24 h, NbC/Nb/SS304 increase by just 0.42 mΩ·cm2 (from 8.76 mΩ·cm2 to 9.18 mΩ·cm2). However, Nb/SS304 increase by 1.2 mΩ·cm2 (from 14.0 mΩ·cm2 to 15.2 mΩ·cm2) and SS304 increase by 64 mΩ·cm2 (from 224 mΩ·cm2 to 288 mΩ·cm2). Moreover, the hydrophobic angle of NbC/Nb/SS304 is 116.5°, compared to Nb/SS304 (108.8°) and SS304 substrate SS304 (67.5°), which is beneficial to the drainage of the PEMFC.

Investigation of corrosion properties with Ni–P/TiNO coating on aluminum alloy bipolar plates in proton exchange membrane fuel cell

Aluminum alloy bipolar plates have unique application potential in proton exchange membrane fuel cell (PEMFC) due to the characteristics of lightweight and low cost. However, extreme susceptibility to corrosion in PEMFC operation condition limits the application. To promote the corrosion resistance of aluminum alloy bipolar plates, a Ni–P/TiNO coating was prepared by electroless plating and closed field unbalanced magnetron sputter ion plating (CFUMSIP) technology on the 6061 Al substrate. The research results show that Ni–P interlayer improves the deposition effect of TiNO outer layer and increase the content of TiN and TiOxNy phases. Compared to Ni–P and TiNO single-layer coatings, the Ni–P/TiNO coating samples exhibited the lowest current density value of (1.10 ± 0.02) × 10−6 A·cm−2 in simulated PEMFC cathode environment. Additionally, potential cyclic polarization measurements were carried out aiming to evaluate the durability of the aluminum alloy bipolar plate during the PEMFC start-up/shut-up process. The results illustrate that the Ni–P/TiNO coating samples exhibit excellent stability and corrosion resistance.

Investigation of acidity on corrosion behavior and surface properties of SS304 in simulated PEMFC cathode environments

This study presents the influence of acidity on the corrosion performance and surface properties of AISI 304 stainless steel (SS304) in the simulated cathode condition of proton exchange membrane fuel cells (PEMFC) with various concentrations of H2SO4. The electrochemical tests indicate that the corrosion resistance of SS304 samples decreases gradually with the solution acidity ascending, but the stable current densities (0.043–0.547 μA cm−2) in the simulated solutions after polarization (0.6 V, 5 h) are all lower than that of the relevant DOE 2025 target (icorr < 1 μA cm−2). Obvious pitting corrosion occur in the solutions with H2SO4 concentration higher than 10−3 M. The surface wettability and interfacial contact resistance (ICR) of the potentiostatically polarized SS304 show an upward trend with the solution acidity increasing, and whether the SS304 samples are polarized or not, their ICR (0.274–1.232 Ω cm2) is far higher than the latest DOE 2025 technical target (<0.01 Ω cm2). The results reveal that surface modification is indispensable for SS304 as bipolar plates, and more attention should be paid to possessing high and stable pitting resistance, hydrophobicity, and interfacial conductivity in an acid environment.

Study on Corrosion Resistance and Conductivity of TiMoN Coatings with Different Mo Contents under Simulated PEMFC Cathode Environment.

TiMoN coatings with different Mo contents on a SS316L substrate are deposited by using closed field unbalanced magnetron sputtering ion plating (CFUMSIP) technology to enhance the corrosion resistance and durability of stainless steel (SS) bipolar plates (BPs) in proton exchange membrane fuel cell (PEMFC) during the start-up/shut-down process. The electrochemical test results illustrate that TiMoN-4A coating has extremely good corrosion resistance compared to other coatings. The potentiostat polarization (+0.6 VSCE) tests indicate that the corrosion current density (Icorr) of TiMoN-4A coating is 5.22 × 10−7A cm−2, which meets the department of energy 2020 targets (DOE, ≤1 × 10−6 A cm−2). Otherwise, TiMoN-4A coating also exhibits the best corrosion resistance and stability in potentiostatic polarization, electrochemical impedance spectroscopy (EIS), and high potential (+1.2VSCE) polarization tests. The interfacial contact resistance (ICR) measurement results show that TiMoN-4A coating has the minimum ICR of 9.19 mΩ·cm2, which meets the DOE 2020 targets (≤10 mΩ·cm2).

Performance of SS304 Modified by Silver Micro/Nano-Dendrite Coating with Hot-Water Super-Repellency in Simulated PEMFC Cathode Environment.

In this study, an silver (Ag) plating with micro/nano-dendrite structures is prepared on the 304 stainless steel (SS304) surface by potentiostatic deposition (Ag/SS304). After being modified by n-dodecyl mercaptan (NDM) with the low surface energy, the obtained sample (NDM@Ag/SS304) exhibits stable superhydrophobicity and excellent hot-water repellency. The surface morphology and composition of NDM@Ag/SS304 are analyzed by scanning electron microscope (SEM), X-ray spectrometer (EDS), X-ray diffractometer (XRD), and X-ray photoelectron spectrometer (XPS) characterization. The electrochemical measurements, tests of water contact angle (WCA), and interfacial contact resistance (ICR) are employed to systematically study the performance of the NDM@Ag/SS304 in the simulated cathode environment of proton exchange membrane fuel cell (PEMFC). The results show that the NDM@Ag/SS304 has high corrosion potential (~0.25 V) and low corrosion current density (~4.04 μA/cm2); after potentiostatic polarization (0.6 V, 5 h), the NDM@Ag/SS304 also shows high superhydrophobic stability.

Nanometric CrN/CrAlN and CrN/ZrN multilayer physical vapor deposited coatings on 316L stainless steel as bipolar plate for proton exchange membrane fuel cells

Nanometric CrN/ZrN and CrN/CrAlN multilayer coatings were deposited on 316L stainless steel as metallic bipolar plates (BPs) for proton exchange membrane fuel cells (PEMFCs) by the cathodic arc evaporation-physical vapor deposition technique. The coatings were evaluated using X-ray diffraction, field emission scanning electron microscopy, surface roughness determination, and water droplet contact angle measurement. In order to study the electrochemical behavior of the coatings, potentiodynamic polarization and electrochemical impedance spectroscopy examinations were conducted at the simulated cathodic PEMFC media (0.5 M H2SO4 purging O2, 70°C). Also, the interfacial contact resistance (ICR) of the coated and uncoated 316L BPs was evaluated in different compaction forces before and after the potentiostatic polarization test. The current density at 0.644 V vs. Ag/AgCl of 0.16 and 0.76 μA cm−2 was recorded for CrN/ZrN and CrN/CrAlN, respectively. Moreover, it was found that after the potentiostatic polarization tests, the ICR values of the 316L BPs were decreased from 276 to 8.3 and 9.4 mΩ cm2 by the deposition of the CrN/ZrN and CrN/CrAlN coatings, respectively. The enhancement in the ICR and corrosion behavior of both CrN/ZrN and CrN/CrAlN multilayer coatings indicated that these coatings can be potentially suitable for PEMFCs application, according to the United States Department of Energy's targets.

Doping and stress induced failure of Ti(Al/Pt)N films on Ti6Al4V plate in a simulated PEMFC environment

Ti(Al/Pt)N films prepared on Ti6Al4V (TC4) plates were soaked in a simulated proton exchange membrane fuel cell (PEMFC) anode environment for three weeks. The dense Ti(Al/Pt)N films exhibited various preferred orientations: TiN and TiAlN films with (111) and TiAl(Pt)N film with (200) orientations. The inner stresses of the Ti(Al/Pt)N films changed from −13 MPa for TiN, −115 MPa for TiAlN, and −66 MPa for TiAl(Pt)N. The corrosion current densities of TiN, TiAlN, and TiAl(Pt)N were of the order of 10−8, 10−7 and 10−6 A·cm−2, respectively. Their corresponding contact resistance values decreased sequentially from 29.85, 15.25 and 9.85 mΩ cm2. The appearance of second EIS impedance circles after soaking the films in the simulated PEMFC environment for 3 weeks was indicative of the corrosion failure of the Ti(Al/Pt)N films. The relatively high inner stress in the TiN film led to the formation of oxides and corrosion pits. Peeling of the TiAlN film off the TC4 occurred owing to the high inner stress. The micro-potential difference between the TiAlN columns and Pt particles that were distributed along the column boundary led to the formation of crack networks in the TiAl(Pt)N film. Al/Pt in TiN deteriorated the durability of the films, although it enhanced their conductivity.